Inter-string arrays of bimetallic assemblies with alternative Cu2+-Cl-Cu2+ and Cu-NC-M (M = Co3+, Fe+3, Cr+3) bridges:: Syntheses, crystal structure, and magnetic properties

Three bimetallic assemblies with alternate homometallic bridges through chloride ligands and heterometallic bridges through cyanide ligands of formula [(323)(2)Cu-2(Cl)M(CN)(6)]n(.)2n(H2O), where 323 = N,N-bis(3-aminopropyl)ethylenediamine and M = Co3+ for 1, Fe3+ for 2, and Cr3+ for 3, were synthesized. They have been characterized structurally, analytically, spectroscopically, and magnetically. All three assemblies crystallize in the monoclinic system in the same space group P2(1)/n, with a = 11.642(2) Angstrom, b = 10.285(3) Angstrom, c = 13.622(2) beta, = 95.69(3)degrees, V = 1623.1(6) Angstrom(3), and Z= 4 for 1; a = 11.681(4) Angstrom, b = 10.315(3) Angstrom, c = 13-567(5) Angstrom, beta = 95.62(3)degrees, V = 1626.8(9) Angstrom(3), Z = 4 for 2, and a = 11.782(4) Angstrom, b = 10.386(2) Angstrom, c = 13.755(4) Angstrom, [3 = 95.51(3)degrees, V = 1657.4(8) Angstrom(3), Z = 4 for 3. Crystal structure analyses reveal that one-dimensional zigzag chains propagate in two different crystallographic directions (a and b) which are held together during the course of their propagation. All three assemblies have a homometallic Cu-Cl-Cu core in common. Assembly 1 exhibits metamagnetic behavior and shows weak antiferromagnetic interactions between Cu2+ paramagnetic centers, through the chloride bridges. The Neel temperature, T-N, is 3.5 K, and the critical field is 4 T. In the presence of a magnetic field larger than 4 T, the local spin doublets of Cu2+ in the assembly 1 remain in parallel arrangements. Assemblies 2 and 3 may be described as an alternative repetition of the antiferromagnetically coupled Cu-Cl-Cu fragment and ferromagnetically coupled Cu-CN-Fe3+/Cr(3+)fragment. The overall magnetic character of the strings in assemblies 2 and 3 are antiferromagnetic. Ferromagnetic interaction evidenced by the (Cu-CN-Fe3+/Cr3+) fragment was masked by the antiferromagnetic interaction between the Cu2+ centers through the chloride bridge. The magnetic properties agree well with those expected for two [323 Cu2+] and a [Fe(CN)](3+) unit with spin-orbit coupling effect of the low-spin iron(III) ions for 2 and for two [323 Cu2+] and a [Cr(CN)](3+) unit for 3. In aqueous solution, trinuclear [(323)(2)Cu2M(CN)(6)](+) and dinuclear [(323)CuM(CN)(6))(-) species were observed.